Affiliations

Research

Malaria is a leading cause of death in tropical and subtropical regions. The Plasmodium parasite that causes malaria is transmitted by the biting of female Anopheles mosquitoes. In Africa, the major mosquito vector is Anopheles gambiae. Females of this species have a high reproductive capacity that is ensured by a single mating event (Fig. 1). The dependence of this mosquito species on a single mating event for reproduction makes targeting reproductive biology a promising strategy for future vector control.

Our group studies the molecular basis of mating and reproduction in both the female and male Anopheles gambiae mosquito. During mating, males transfer sperm (which is stored in the female sperm storage organ – the spermatheca), along with protein secretions in the form of a gelatinous rod – the mating plug. Post mating, the plug is broken down in the female reproductive tract; this processing also coincides with major behavioral and physiological changes. The female becomes refractory to further mating, egg laying is triggered in blood fed females, and the atrium itself undergoes extensive morphological changes.

Figure 1. Anopheles gambiae mosquitoes during mating. The male mosquito on the left and a bloodfed female on the right. Photo courtesy of Sam Cotton UCL.

Previous work from our group began to dissect the genetic basis of the events that are triggered by copulation. We have identified large transcriptional and morphological changes in the female mosquito after mating (Rogers et al. 2008). Our efforts are now focused on understanding how these changes correlate with the onset of post-mating responses in females, and to this aim we are using RNAi-mediated gene silencing to target a number of candidate genes that may play a role in mosquito reproduction. Our studies are starting to provide insight into the pathways involved in the events triggered by copulation.

As females mate a single time and therefore are not capable of replenishing their sperm stores, targeting sperm storage would reduce reproductive success and have a strong impact on the size of mosquito populations. We are therefore studying the pathways involved in protecting sperm from damage during long-term storage as these may provide good targets for genetic manipulation and/or chemical inhibition. We are also performing pathways analysis to dissect the signaling cascades triggered by copulation, which underlie important post mating responses.

Research from our group has also highlighted male factors that are essential for reproductive success. We have determined that the transfer of seminal secretions in the form of a mating plug is essential for correct sperm storage, identifying the plug as a key player of mosquito fertility and a good target for manipulation of fertility of field populations (Rogers et al. 2009). Through the development of spermless males, we have been able to determine that sperm do not play a role in modulating female post-mating behavior (Thailayil et al. 2011). Work is ongoing to identify the specific male molecular factors crucial to mating success.

Overall we aim to provide insight into the reproductive biology of this malaria vector, which until recently remain largely unstudied, so that new targets for vector control can be developed.